Electronic devices often need to generate multiple power regimes while only being powered by a single source. For example, a laptop computer may only have a single battery but may need to produce power regimes with different supply voltages for the various components on the laptop. Furthermore, regardless of the need for multiple power regimes, electronic devices often need to condition the power that is delivered to them from an external source. Returning to the example of a laptop, the laptop processor contains sensitive electronics and exhibits a widely varying power demand based on how hard the processor is working. Simply plugging in a DC version of the mains voltage source is not an option because the processor will not be shielded from dips or surges in the power supply and the power supply will likewise not be able to keep pace with the rapid transitions in the power drawn by the processor. The aforementioned requirements are addressed by power converters.
FIG. 1 provides a block diagram of an example power converter 100 with the input of the power converter being provided by supply 101 and the output of the power converter being provided to load 102. In this example, the input is a voltage VIN provided on an input node of the power converter, and the output is a voltage VOUT provided on an output node of the power converter. Power converter 100 will, therefore, regulate the output by keeping VOUT at a target voltage despite variation in the current drawn by load 102 or the voltage provided by supply 101. Alternative power converters may regulate an output current while allowing a voltage at the output node of the converter to vary.
Switched mode converters are a specific class of power converters that utilize a switching circuit and an output filter to control the transfer of power from the input regime to the output regime. In the illustrated example, power converter 100 utilizes switching circuit 103 and an output filter that comprises inductor 104 and capacitor 105. The current through inductor 104 is labeled iL and the current provided to the load is labeled iOUT. The switching circuit 103 is itself coupled to the input node and serves to couple power converter input side 107 to power converter output side 108. One way the power converter can achieve regulation of the output is through the use of a control loop that controls the switching of switch circuit 103. As illustrated, the control loop includes a feedback path 106 that provides a control signal to switching circuit 103 that is based on a measurement taken from output side 108.
Power converters can operate in different modes based on various factors such as the operating point of the converter. For example, if load 102 dramatically decreased the amount of power it required from supply 101, power converter 100 could be switched into a low power operating mode to preserve efficiency while still regulating the output. While benefits are provided by switching to different modes based on the operating point of the converter, transitioning between modes can disrupt the regulation of the power converter. These disruptions can cause the regulated output to deviate from its desired value by an unacceptable degree. Some of these disruptions are referred to as output overshoot, output undershoot, and unacceptably high ripple current in the power converter.